Paralytic shellfish toxins (PSTs) are non-protein neurotoxins produced by saltwater dinoflagellates and freshwater cyanobacteria. The ability of Lactobacillus rhamnosus strains GG and LC-705 (in viable and non-viable forms) to remove PSTs (saxitoxin (STX), neosaxitoxin (neoSTX), gonyautoxins 2 and 3 (GTX2/3), C-toxins 1 and 2 (C1/2)) from neutral and acidic solution (pH 7.3 and 2) was examined using HPLC. Binding decreased in the order of STX ~ neoSTX > C2 > GTX3 > GTX2 > C1. Removal of STX and neoSTX (77%–97.2%) was significantly greater than removal of GTX3 and C2 (33.3%–49.7%). There were no significant differences in toxin removal capacity between viable and non-viable forms of lactobacilli, which suggested that binding rather than metabolism is the mechanism of the removal of toxins. In general, binding was not affected by the presence of other organic molecules in solution. Importantly, this is the first study to demonstrate the ability of specific probiotic lactic bacteria to remove PSTs, particularly the most toxic PST-STX, from solution. Further, these results warrant thorough screening and assessment of safe and beneficial microbes for their usefulness in the seafood and water industries and their effectiveness in vivo.

Viable, heat-and acid-killed Lactobacillus rhamnosus strain GG (LGG) has shown high binding properties with zearalenone (ZEN). To identify the type of chemical moieties and interactions involved in binding with the ZEN, LGG was subjected to different chemical and enzymatical treatments, prior to the binding experiments. Pretreating the viable, heat- and acid-killed bacteria with m-periodate significantly decreased ZEN binding, suggesting that ZEN binds predominantly to carbohydrate components. Pretreatment with Pronase E had no effect on the ability of viable cells to bind ZEN, however, a reduction in the binding of ZEN by heat- and acid-killed cells, suggesting that the new binding sites exposed by heat or acid are proteins in nature. Pretreatment with urea also decreased binding, suggesting that hydrophobic interactions play a role in ZEN binding. The binding of ZEN in concentrations ranging from 0.79 to 62.82 microM and its subsequent dissociation by repetitive aqueous washes was also studied. The binding sites of the bacteria were not saturated by the maximum ZEN concentration studied.

The papers in these proceedings truly reflect the wide nature of research work that is being undertaken and the advances that have been achieved particularly in the therapeutic application of probiotics. All abstracts are available as pdf and html format.

The interaction of a potent carcinogen, aflatoxin B1 (AFB1), with a probiotic strain of lactic acid bacteria, Lactobacillus rhamnosus strain GG (GG), has been investigated. The binding of AFB1 to GG in the late exponential–early stationary phase was studied for viable, heat-killed and acid-killed bacteria. In general, viable, heat-killed and acid-killed GG responded in a similar manner. The effects of pronase E, lipase and m-periodate on AFB1 binding and release were consistent with AFB1 binding predominantly to carbohydrate components of the bacteria. The effect of urea suggested hydrophobic interactions play a major role in binding. Increasing concentration (0.01–1 M) of NaCl or CaCl2 had minor effects on AFB1 binding suggesting some involvement of electrostatic interactions. An increase in pH from 2.5 to 8.5 had no effect on AFB1 binding but decreased binding of AFB2a, possibly due to hydrogen bonding interactions.